The present invention relates to an improved signal apparatus, that is a device that is used to alert a person to the happening of some particular event. The signal device of the present invention is based on the balance beam concept and is intended to provide a signal when a bag used to collect blood at a blood bank is full and needs to be disconnected from a donor. In the illustrated embodiment, an audible signal is given by a bell that is actuated by the movement of a counter-weighted arm when the bag at one end of the arm is full.
Signal devices of various kinds are well known in the prior art, as illustrated by U. S. Pat. No. 2,143,706 issued to 14 Alcide E. Mathey on Jan. 10, 1939 which shows a device that provides an audible signal to an operator when liquid in a tank reaches a predetermined level. U. S. Pat. No. 2,897,853 which issued on August 4, 1959 to Roland W. Anstine shows a filling indicator assembly for use with underground tank installations to indicate the level of liquid to which tanks are being filled. U. S. Pat. No. 2,212,620 which issued on Aug. 27, 1940 to Frank P. Sculley, et al. shows another device for indicating to an operator by audible signal means that the level of liquid in a tank has reached a predetermined level, so that the supply of liquid into the tank can be cut off in time to prevent overflow. U. S. Pat. No. 531,557 which issued on Dec. 25, 1894 to Eugen C. Paetow shows an alarm that is actuated when a certain level of liquid is collected in a pan. U.S. Pat. No. 954,423 which issued to Ernest A. Cramer on April 12, 1910 shows a fluid level indicator for use with lamps, and U.S. Pat. No. 1,441,191 which issued on Jan. 2, 1923 to Benjamin Weiss shows an improvement to signaling devices which provides for an alarm to be sounded repeatedly at intervals.
The present invention provides a novel and useful alarm apparatus that is uniquely adapted for use in the drawing of blood at blood banks